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R. M. LOCKWOOD & S. H. BARTLETT. Transmitter fOr Telephones.

826. Patented June 15,1880.

INVEN'EJRS l @fm www N.PEIERS. PHDTOALITNOGRAMER, wAsHlMnTON. D-

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PATENT ROBERT M. LOOKVOOD AND SAMUEL H. BARTLETT, OF NEW YORK, N. Y., ASSIGNORS OE ONE-HALF OF THEIR RIGHT TO CHARLES F. LIVERMORE,

OF SAME PLACE.

TRANSMITTER FOR TELEPHONES.

SPECIFICATION forming part of Letters Patent No. 228,826, dated June 15, 1880.

Application filed November 3, 1879.

, To 'all whom it may concern:

Be it known that we, ROBERT M. LOCK- wooD and SAMUEL H. BAn'rLE'r'r, bot-h of the city, county, and State of New York, have invented certain Improvements in Transmitters for Telephones, of which the following is a specication.

This invention differs essentially from telephonic transmitters hitherto devised, for the 1o reason that its effectiveness depends not upon the vibration or movement bodily of a diaphragm or equivalent to which the soundwaves of the air are directed, but upon a movement which may be termed molecular, inasmuch as it is transmitted from. molecule to molecule of anon-resonant transmitting material, which, as a body,remains stationary while serving as a conducting agent between the aerial sound-waves and the microphone which 2o controls the volume, pitch, and variation of sound transmitted to and through the wires.

In the practice of the invention a microphone of any suitable character, and provided with suitable transmitting-wires, is supported and partially embedded in cork or light wood or other equivalent non-resonant material, so that when the sound-waves produced from the voice or other sound-producing agent are directed against the external surface of the non-resonant material a molecular disturbance in the structure of said material is set up, which, being communicated to the microphone, causes a similar disturbance therein, which, in its turn, modies the conducting action of the Voices in a proportionate degree, so that the original sound, modified as a manifestation of force in the course of its transmission, is reproduced at other portions of the circuit in a receiver of any appropriate kind.

Figures l, 5, and 6 are sectional views representing a telephonie transmitter embracing our said invention. Figs. 2 and 3 show, in plan View, the parts included in Fig. l; and Fig. 4 shows certain of the parts included in Fig. 6.

The microphone is composed of the two bars A A, the inner ends of which approach each other, but have a greater or less space between them. These bars are preferably of carbon,

ofthe kind well known to electricians, but may 5o be of metal, which latter, however, so far as our experiments have extended, has been shown to be inferior to carbon. At `or near the outer ends of these bars are attached suitable telephonie wires A A.

In the construction shown in Figs. l, 2, and 5 the adjacent ends ofthetwo bars are hollowed out so as to provide between them a circular opening, b. This opening receives the wooden stem c of a button, B, (said stem may 6o be of any material not a conductor of electricity,) which should be of carbon or of other material suitable for the bars A A. The button B rests by gravity upon the upper surface of the inner ends of the bars A A.

The bars AA are embedded in or surrounded by a mass, O, of cork 5 or in lieu thereof, (but with inferior utility,) a mass of light wood or other non-resonant material possessing, so far as may be, the peculiar property of the cork, as hereinafter explained.

It is to be observed that the mass of nonresonant material C is chambered, as shown at B', said chamber receiving the inwardlyprojecting inner ends of the bars, and also the button B, resting thereon.

In theoperation of the apparatus the soundwaves produced in the air by the voice or other sound -producing agent strike the external surface of the cork, but from the inertness of 30 the cork to vibratory action produce no vibration therein, but, on the contrary, transmit their force from molecule to molecule of the non-resonant mass, until the molecular motion reaches and is transmitted to the bars A A, and thence to the button B or its equivalent; but inasmuch as the degree of this molecular force varies with that of the impact on the external surface of the cork, it follows that the molecular action, in passing from the bars to the button, will be more or less modified, inasmuch as the surfaces of contact between the button, and the bars provide different conditions from those afforded in the homogeneous material of the bars themselves. This modification or disturbance in the relation of the button to the bars, although incapable| of mechanical measurement, and itself consisting rather in a ehan ged condition ot" thepoiuts of contact of the touchingfsurface than in any change in their relative position, is responsive to every modification in the sound waves brought to bear against the external surface of the cork, and the microphone, being thus responsive to every variation in the original sound, insures its transmission through the wiresto any ordinary or appropriate receiver.

The office of the wooden pin in the button B is simply to reta-in the latter in position, the

Y flat surface ofthe button restin upon the iiat surfaces of the bars being found to give, upon the whole, better results than any other relation of the parts thus far devised.

The same results may be obtained by means of a cavity formed in and between the adjacent ends of the bars, to secure a simple ball or sphere of carbon or other suitable material,

as shown in Figs. 4 and 6; but the wedging oi"A the ball in the socket is found, with this con struction, to render its performance somewhat inferior to that of the button made as hereinbefore described.

W'hen desired, the non-resonant material C may be confined between two metal plates or blocks, D D, as shown in Fig. 5.

Ve donot limit ourselves to the precise means herein described for carrying into effeet our said invention, inasmuch as the same may be widely varied by the exercise of the judgment of persons fairly skilled in the art to which our said invention relates, andinasmuch as we believe ourselves to be the first to devise a practical telephonie transmitter dependent for operation, not upon vibration or vibratory action, but upon themolecular trans mission ot' force through a suitable non-resonant material.

Ve do not herein claim embedding the carbon plates or conductors wholly in a non-resonant substance, as that feature is made the subject of another application led by us March 9, 1880; but

Plates orbars ofcarbon or other conducting material arranged with their adjacent sides or ends out of contact, and having their oppo-` site sides or ends firmly supported in a nonresonant material, in combination with the interposed button, arranged and operating substantiall y as described.

R. M. LOGKWOOD. SAML. H. BARTLETT.

Witnesses Trios. J. FARRELL, Grms. H. DoXAfr. 

